1. Field of the Invention
The present invention relates to a biosensor capable of rapidly quantifying a specific component in a sample, particularly a biological sample, with high accuracy in a simplified manner, and to a method for producing the same.
2. Description of the Prior Art
Heretofore, as a system capable of rapidly quantifying the specific component in a sample solution with high accuracy, there has been known a biosensor (for instance, Japanese Laid-Open Patent Publication No. Hei 3-202,764) which will be described below.
The disclosed conventional biosensor is configured by forming an electrode system composed of a measuring electrode and a counter electrode on an electrically insulating base plate, then forming thereon a reaction layer comprising a hydrophilic polymer, an oxido-reductase and an electron acceptor, and thereafter forming a hollow space constituting a sample supplying channel of the sensor by combining a cover and a spacer with the base plate.
When the sample solution containing a substrate to be quantified is contacted with an inlet of the sample supplying channel, the sample solution is rapidly introduced into the reaction layer due to a capillary phenomenon of the above-mentioned hollow space to dissolve the reaction layer. Then, the substrate is allowed to react with the enzyme contained in the reaction layer and the electron acceptor is reduced. Upon completion of the enzyme reaction, the reduced electron acceptor is electrochemically oxidized to produce an oxidizing current, and based on the value of the oxidizing current obtained with this oxidation reaction, the concentration of the substrate contained in the sample solution can be determined.
Further, the disclosed biosensor is produced by the steps of forming the electrode system on the base plate, forming the reaction layer on the electrode system and combining the cover and the spacer with the base plate, the electrode system and the reaction layer to form the hollow space.
In the configuration of such prior art biosensor, the hollow space formed between the cover and the base plate is tubular-shaped, and therefore the supplied sample solution only contacts a part of the reaction layer that is substantially identical with an outer shape of the electrode system. Therefore, an area occupied by the region of the reaction layer actually dissolved in the sample solution can never be made constant, thereby to create a cause for deteriorating a sensor response-reproducibility of the sensor. Further, according to a production method composed of forming the reaction layer by titrating a solution containing the oxido-reductase on the electrode system and drying the titrated solution, it is difficult to form a homogeneous reaction layer because of overflowing of the solution outside the electrode system.